Electrical conductivity in the early universe

We solve numerically the Boltzmann equation in the early universe in the presence of a constant electric field and find the electrical conductivity $\sigma$ in the range $1\MeV\lsim T\lsim M_W$. The main contribution to $\sigma$ is shown to be due to leptonic interactions. For $T\lsim 100\MeV$ we find $\sigma\simeq 0.76T$ while at $T\simeq M_W$ we obtain $\sigma\simeq 6.7T$